Zoom lens

ABSTRACT

A zoom lens having a range of equivalent focal lengths extending from a range below the dimension of the diagonal of the image frame to a dimension substantially above and having a zooming range of up to six to one or greater where the lens has a plus, minus, plus, plus lens unit configuration with a strongly negative second lens unit and a fourth lens unit designed to have a given power and telephoto ratio to compensate for a remote aperture stop located in the third lens unit.

FIELD OF THE INVENTION

This invention relates to zoom lenses and, more particularly, relates to zoom lenses having a range of equivalent focal lengths (EFL) from a dimension below the diagonal of the image frame to a long focal length which may be as great as six times the diagonal of the image plane.

BACKGROUND OF THE INVENTION

Wide angle to long focal length zoom lenses have been available for some time. However, there is a constant effort to design such lenses which are more compact, while having a relatively fast aperture. These wide angle to long focal length zoom lenses require different design considerations than a so-called telephoto zoom lens, which, in the thirty-five millimeter format, may be a 70-210 millimeter zoom lens, as exemplified in U.S. Pat. No. 3,817,600.

In the telephoto zoom lenses, it is customary that a rear stationary lens unit have a low telephoto ratio, generally less than one, and the aperture defining iris is included in this rear stationary lens unit. The telephoto ratio is the ratio of the equivalent focal length of the lens or lens lens unit to the front vertex distance (FVD), where the front vertex distance is the distance from the front apex of the lens to the image plane, generally when the lens if focused to infinity. An example of a widely used wide angle to long focal length zoom lens is disclosed in U.S. Pat. No. 4,299,454.

It is common practice to use a basic triplet or variation thereof as a rear lens unit in a zoom lens. The optical powers of a triplet are in a plus-minus-plus configuration separated by small air spaces. The lens units may be subdivided or compounded, but the overall shape remains biconvex. The positive lens units may be and often are meniscus shaped. A triplet, in its simplest form, can be corrected for all primary aberrations, and is particularly well suited for large aperture requirements; however, it is limited with respect to angular coverage because of inherent astigmatism.

In wide angle to long focal length zoom lenses, where the rear lens unit moves to vary the EFL, the iris defining aperture cannot be placed in the rear lens unit. Otherwise, the diameter of the front of the lens would become excessive.

The fourth lens unit thus has to operate with the handicap of having a removed aperture stop. Generally, in wide angle to long focal length zoom lenses utilizing four lens units, a compromise is made in that the aperture stop is positioned closely adjacent the third lens unit and may move with the third lens unit, as disclosed in U.S. Pat. No. 4,299,454, or may remain stationary with the third lens unit, as disclosed in U.S. Pat. No. 4,256,381. If the aperture stop is positioned too far away from the rear lens grouping, it becomes very difficult to control aberration correction without a complex rear lens unit, sacrificing compactness.

A major design constraint of the wide angle to long focal length zoom lens is the size of the rear lens opening. Typically, the clear aperture must be less than thirty millimeters (24×36 mm image size). In the wide angle position, light rays pass through the third lens unit at a large angle to the optical axis normally requiring large clear apertures of the elements of the fourth lens unit. If compactness of the lens is not emphasized, then the optical power of the fourth lens unit need not be large and the size of the opening of the fourth lens unit is not so critical. However, in the use of the thirty-five millimeter camera, lens compactness is a primary concern.

Accordingly, the present invention provides a four lens unit wide angle to long focal length zoom lens of plus, minus, plus, plus configuration, having a new and improved design in the fourth lens unit which compensates for the problem of a remote aperture stop, and diameter of the fourth lens unit, and which is relatively simple in a design that contributes to the compactness of the overall lens.

SUMMARY OF THE INVENTION

The present invention is directed to a wide angle to long focal length zoom lens of the types shown in U.S. Pat. Nos. 4,299,454 and 4,256,381. The aforementioned patents disclose wide angle to long focal length zoom lens comprising a first positive lens unit, a second very strong negative lens unit, a third positive lens unit, and a fourth positive lens unit. In commercial forms of these lenses, generally the first and fourth lens units move in the same direction for zooming, while the second lens unit moves in a direction opposite to the direction of movement of the first and fourth lens units. The third lens unit may move or may remain stationary. Alternatively, the second lens unit may be fixed and the third lens unit move in fixed relation to the aperture defining iris. A characteristic of this form of lens is its very strong negative second lens unit. This contributes to the compactness of the lens over a wide range of equivalent focal lengths (EFL) which may be greater than five to one. Typically, the second negative lens unit may have an absolute power which has a ratio to the geometric mean of the extremes of the EFL's of the lens as great as five to one.

The present invention provides zoom lenses which may have a zoom ratio of over six to one, using a four lens unit configuration of plus, minus, plus, plus configuration. The lens is arranged with the iris defining aperture positioned with the third lens unit in fixed relation thereto. The fourth lens unit comprises a first sub lens unit, which is a positive element followed by a doublet comprising a positive element and a negative element. The second sub lens unit may take various forms. However, it is important that the telephoto ratio of the fourth lens unit be within a given range, greater than unity, and the optical power of the lens be within a specified range, as hereinafter disclosed. The disclosed lens form is one in which the first and fourth lens units move in the same direction during zooming, and most often in fixed relation.

An object of this invention is to provide a new and improved zoom lens of the type described.

Another object of this invention is to provide a zoom lens of the type described having a new and improved fourth lens unit which contributes to compactness of the lens.

The features of the invention which are believed to be novel are particularly pointed out and distinctly claimed in the concluding portion of this specification. However, the invention, both as to its organization and operation, together with further objects and advantages thereof, may best be appreciated by reference to the following detailed description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-8 are schematic side elevations of lenses embodying the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Lenses embodying the invention comprise four lens units, G1, G2, G3, and G4, as exemplified in all figures of the drawings. The lens units are referenced as G1-G4 from the object end to the image end.

Lens elements are identified by the reference L followed by an arabic numeral progressively from the object end to the image end of the lens.

Lens element surfaces are identified by the reference S followed by an arabic numeral progressively from the object end to the image end of the lens.

The focal plane of the lenses shown in the drawings are denoted by the reference FP and the optical axis by A. The prescriptions of all lenses set forth in the Tables II-IX are scaled to an image format of 24×36 mm.

In FIGS. 1-6, lens unit G1 comprises a biconvex doublet L1, either air spaced or cemented, L2, and a positive meniscus L3.

In FIGS. 1-6, the second lens unit G2 comprises a negative meniscus L4, a biconcave component L5, and a doublet comprising a positive element L6 concave to the object and a negative element L7. Lens having the configuration of this second negative lens unit are disclosed and claimed in U.S. Pat. No. 4,299,454, assigned to the same assignee as the present invention.

The third lens unit G3 in all cases is positioned in fixed relation to the aperture defining iris I. In FIGS. 1, 2, 4, and 6, lens unit G3 is a doublet comprising a biconvex element L8 and a meniscus L9 concave to the object In FIG. 3, lens unit G3 is a single element L8. In FIG. 4, lens unit G3 comprises a biconvex element L8, followed by a biconvex doublet L9, L10.

Lens unit G4 in all examples consist of first and second sub lens units, hereinafter designated in Table I as G4a and G4b, respectively. The first sub lens unit comprises a positive element L10 in FIGS. 1, 2, 4, and 6, L9 in FIG. 3, and L11 in FIG. 5. This positive component is followed by a doublet L11, L12 (FIGS. 1, 5, and 6), L12, L13 (FIG. 4), L10, L11 (FIGS. 2 and 3), either cemented or air spaced as shown in FIGS. 1 and 3, which comprises a positive element and a negative element.

The second sub lens unit comprises two elements, L13, L14 (FIGS. 1, 2, 4, and 6), L12, L13 (FIG. 3), L15 (FIG. 5).

In FIG. 7, lens unit G1 comprises a biconcave element L1, followed by two biconcave elements L2 and L3. Lens unit G2 consists of a negative meniscus L4, convex to the object and a doublet comprising biconcave element L5 and a positive meniscus L6. Lens unit G3 comprises a positive element L7 convex to the object and a meniscus concave to the object. In lens unit G4 the first sub lens unit comprises a biconvex element L9 followed by a cemented doublet in the form of positive meniscus L11 convex to the object and a negative meniscus L11 also convex to the object. The second sub lens unit consists of a single meniscus L12 having an aspheric surface S21.

The lens of FIG. 8 has a front lens unit G1 comprising elements L1, L2 and L3 in a configuration the same as FIGS. 2 and 3. The second lens unit G2 comprises elements L4, L5 and L6 in the same configuration as FIG. 7. Lens unit G3 comprises elements L7 and L8 in the same configuration as FIG. 7. The first sub lens unit of lens unit G4 comrpises elements L9, L10 and L11 in the same configuration as FIG. 7 while the second sub lens unit consists of a biconcave element L12 and and biconvex element L13. The surface S22 of L12 is aspheric.

The lenses of FIGS. 7 and 8 include an element having at least one aspheric surface defined by the equation ##EQU1## where X is the surface sag at a semi-aperture distance Y from the axis A of the lens, C is the curvature of a lens surface of the optical axis A equal to the reciprocal of the radius of the optical axis, K is a conic constant.

The arrangement of the lens elements in lens units G1-G4 is tabulated and summarized in Table I. The subunits of lens unit G4 are denoted as G4a and G4b.

                  TABLE I                                                          ______________________________________                                         G1         G2       G3       G4a     G4b                                       ______________________________________                                         FIG. 1 L1-L3   L4-L7    L8,L9  L10-L12 L13,L14                                 FIG. 2 L1-L3   L4-L7    L8,L9  L10-L12 L13-L15                                 FIG. 3 L1-L3   L4-L7    L8     L9-L11  L12,L13                                 FIG. 4 L1-L3   L4-L7    L8,L9  L10-L12 L13,L14                                 FIG. 5 L1-L3   L4-L7    L8-L10 L11-L13 L14,L15                                 FIG. 6 L1-L3   L4-L7    L8,L9  L10-L12 L13,L14                                 FIG. 7 L1-L3   L4-L6    L7,L8  L9-L11  L12                                     FIG. 8 L1-L3   L4-L6    L7,L8  L9-L11  L12,L13                                 ______________________________________                                    

where G4a and G4b are the front and rear subunits of lens unit G4 respectively.

Lens unit G4 has a telephoto ratio TR, where

    1.5>TR>1.0

The telephoto ratio TR is the ratio of the front vertex distance (FVD) of lens unit G4 to its equivalent focal length. The FVD is the dimension from the front apex of lens unit G4 to the focal plane FP when focused to infinity.

The ratio of the optical power K₄ of lens unit G4 to the geometric mean of the power of the overall lens K_(M) is

    1.7>K.sub.4 /K.sub.M >1.1

Additionally, the optical power K₂ of the second lens unit is very strong, and

    5.0>|K.sub.2 /KM|>1.9

The geometric mean of the power of a zoom lens (K_(M)) is

    √K.sub.S K.sub.L

where K_(S) is the optical power of the lens expressed as the reciprocal of the shortest EFL in millimeters and K_(L) is the optical power of the lens expressed as the reciprocal of the largest EFL in millimeters.

The various lenses disclosed herein may have different movements of the various lens units as hereinafter described. In the tables hereinafter set forth to describe the various lenses, the back focal length (BFL) is the distance from the rear apex of lens unit G4 at the optical axis to the film plane FP. The spacings between the various lens units Z1, Z2, and Z3 are as noted on the drawings and corresponding tables for various focal lengths.

A lens as shown in FIG. 1 is substantially described in Table II. In this lens lens unit G1 and G4 move in fixed relation. Lens unit G2 moves in a direction opposite to lens units G1 and G4, while lens unit G3 has reciprocating motion.

A lens as shown in FIG. 2 is substantially described in Table III. In this lens lens units G1 and G4 move in fixed relation. Group G2 is stationary, and lens unit G3 moves as noted in Table III.

The lens of FIG. 3 is substantially described in Table IV. Lens units G1 and G4 move in fixed relation. Lens unit G3 and iris I are stationary while lens unit G2 moves.

A lens as shown in FIG. 4 is substantially described in Table V. Here the first lens unit G1 and the fourth lens unit G4 move in fixed relation, lens unit G2 moves in the opposite direction and lens unit G3 moves as indicated.

FIG. 5 shows a lens as substantially described in Table VI. Here the first and fourth lens units, G1 and G4 move in the same direction but not in fixed relation. Both of lens units G2 and G3 also move. The iris I moves in fixed relation to lens unit G3.

FIG. 6 shows a lens as substantially described in Table VII. Here the first lens unit G1 and fourth lens unit G4 move in fixed relation, while both lens units G2 and G3 also move as noted in Table VII.

FIG. 7 shows a lens as substantially described in Table VIII. Here the first lens unit G1 and fourth lens unit G4 move in fixed relation. The second lens unit G2 and third lens unit G3 also move as noted in Table VIII. Here surfaces S5 and S22 are aspheric.

FIG. 8 shows a lens as substantially described in Table IX. Here the first lens unit G1 and fourth lens unit G4 move in fixed relation and lens units G2 and G3 move as noted in Table IX. Here surface S22 is aspheric. The aspheric surfaces are provided for purposes of optical correction.

FIG. 1 also exemplifies a lens as described in Table X with minor differences. In Table X, elements L1 and L2 are slightly air spaced and element L13 is of negative power. The lens of Table X has an aspheric surface S24.

                  TABLE II                                                         ______________________________________                                                             AXIAL DISTANCE                                                   SURFACE       BETWEEN                                                    LENS  RADII(mm)     SURFACES(mm)   N.sub.d                                                                             V.sub.d                                ______________________________________                                               S1     160.690                                                           L1                      2.500        1.805                                                                               25.5                                       S2     56.190                                                            L2                      10.270       1.517                                                                               64.2                                       S3     -144.312                                                                                  0.200                                                        S4     40.250                                                            L3                      4.100        1.806                                                                               40.7                                       S5     69.987                                                                                    Z1                                                           S6     61.000                                                            L4                      1.500        1.806                                                                               40.7                                       S7     15.180                                                                                    5.180                                                        S8     -40.000                                                           L5                      1.400        1.773                                                                               49.6                                       S9     49.500                                                                                    0.200                                                        S10    28.000                                                            L6                      7.200        1.673                                                                               32.2                                       S11    -15.415                                                           L7                      1.200        1.773                                                                               49.6                                       S12    -619.000                                                                                  Z2                                                     Aperture                                                                                               1.500                                                        S13    63.588                                                            L8                      3.530        1.697                                                                               48.5                                       S14    -42.087                                                                                   0.480                                                        S15    -30.682                                                           L9                      1.650        1.806                                                                               40.7                                       S16    -64.500                                                                                   Z3                                                           S17    34.420                                                            L10                     4.630        1.581                                                                               40.9                                       S18    -156.800                                                                                  0.200                                                        S19    114.940                                                           L11                     9.390        1.517                                                                               52.2                                       S20    -31.690                                                           L12                     1.220        1.805                                                                               25.5                                       S21    34.420                                                                                    2.480                                                        S22    -88.000                                                           L13                     2.400        1.806                                                                               40.7                                       S23    -38.900                                                                                   0.200                                                        S24    104.500                                                           L14                     2.860        1.806                                                                               40.7                                       S25    -140.000                                                          ______________________________________                                         ZOOM SPACING DATA                                                              EFL     Z1       Z2       Z3     BFLFVD                                        ______________________________________                                          28.83 mm                                                                               1.00 mm 19.33 mm 16.61 mm                                                                              56.93 mm 158.16 mm                             50.01  14.92    11.77    10.25  68.19169.41                                    5.01   26.31     6.24     4.38  78.01179.24                                   131.00  34.52     1.51     0.91  83.26184.48                                   ______________________________________                                    

                  TABLE III                                                        ______________________________________                                                             AXIAL DISTANCE                                                     SURFACE     BETWEEN                                                    LENS    RADII(mm)   SURFACES(mm)   N.sub.d                                                                             V.sub.d                                ______________________________________                                              S1     102.879                                                            L1                      2.300        1.741                                                                               27.8                                      S2     48.694                                                                                     0.500                                                       S3     48.183                                                             L2                      10.400       1.514                                                                               64.2                                      S4     -189.534                                                                                   0.100                                                       S5     43.872                                                             L3                      4.000        1.541                                                                               47.2                                      S6     75.339                                                                                     Z1                                                          S7     84.254                                                             L4                      1.660        1.834                                                                               37.3                                      S8     20.443                                                                                     5.908                                                       S9     -32.836                                                            L5                      1.440        1.773                                                                               49.6                                      S10    57.306                                                                                     0.220                                                       S11    43.367                                                             L6                      7.200        1.717                                                                               29.5                                      S12    -16.903                                                            L7                      1.330        1.773                                                                               49.6                                      S13    -333.557                                                                                   Z2                                                          S14    64.932                                                             L8                      5.000        1.604                                                                               60.2                                      S15    -48.454                                                                                    1.126                                                       S16    -29.934                                                            L9                      2.000        1.673                                                                               32.2                                      S17    -47.916                                                                                    0.500                                                  Aperture                                                                                               Z3                                                          S18    125.580                                                            L10                     3.670        1.648                                                                               33.8                                      S19    -68.714                                                                                    0.180                                                       S20    88.886                                                             L11                     6.000        1.517                                                                               64.2                                      S21    -32.051                                                            L12                     5.500        1.785                                                                               25.7                                      S22    -83.481                                                                                    8.017                                                       S23    118.446                                                            L13                     6.000        1.581                                                                               40.9                                      S24    -42.226                                                            L14                     2.000        1.717                                                                               29.5                                      S25    37.606                                                                                     1.900                                                       S26    341.397                                                            L15                     4.800        1.805                                                                               25.5                                      S27    -95.200                                                            ______________________________________                                         ZOOM SPACING DATA                                                              EFL     Z1       Z2       Z3     BFLFVD                                        ______________________________________                                          38.50 mm                                                                               7.00 mm 19.19 mm 23.74 mm                                                                              48.36 mm 186.24 mm                             73.00  22.36    10.63    13.68  66.89201.50                                   136.00  36.30     4.64     5.02  81.83215.74                                   194.06  42.86     0.59     1.06  89.52221.97                                   ______________________________________                                    

                  TABLE IV                                                         ______________________________________                                                             AXIAL DISTANCE                                                   SURFACE       BETWEEN                                                    LENS  RADII(mm)     SURFACES(mm)   N.sub.d                                                                             V.sub.D                                ______________________________________                                               S1     97.471                                                            L1                      2.000        1.805                                                                               25.5                                       S2     46.414                                                                                    0.961                                                        S3     44.857                                                            L2                      7.500        1.517                                                                               64.2                                       S4     -204.325                                                                                  0.100                                                        S5     33.332                                                            L3                      5.000        1.658                                                                               50.9                                       S6     67.053                                                                                    Z1                                                           S7     48.154                                                            L4                      1.400        1.834                                                                               37.3                                       S8     16.552                                                                                    9.047                                                        S9     -29.301                                                           L5                      1.200        1.773                                                                               49.6                                       S10    37.735                                                                                    0.200                                                        S11    30.244                                                            L6                      5.800        1.673                                                                               32.2                                       S12    -13.650                                                           L7                      1.200        1.773                                                                               49.6                                       S13    -101.590                                                                                  Z2                                                     Aperture                                                                                               1.040                                                        S14    651.451                                                           L8                      2.500        1.834                                                                               37.3                                       S15    -75.022                                                                                   Z3                                                           S16    148.051                                                           L9                      2.664        1.834                                                                               37.3                                       S17    -59.655                                                                                   0.100                                                        S18    17.272                                                            L10                     3.600        1.517                                                                               64.2                                       S19    80.238                                                                                    0.570                                                        S20    -2295.605                                                         L11                     6.060        1.785                                                                               26.1                                       S21    17.700                                                                                    6.307                                                        S22    47.296                                                            L12                     2.000        1.805                                                                               25.5                                       S23    28.126                                                                                    0.931                                                        S24    29.714                                                            L13                     6.000        1.517                                                                               64.2                                       S25    -40.167                                                           ______________________________________                                         ZOOM SPACING DATA                                                              EFL     Z1       Z2       Z3     BFL    FVD                                    ______________________________________                                          35.90 mm                                                                               0.50 mm 10.79 mm 10.77 mm                                                                              49.46 mm                                                                              141.60                                  54.93   9.65     7.07     5.34  53.89  147.03                                  85.00  17.79     2.84     1.43  57.80  150.94                                 101.42  20.76     0.60     0.70  58.53  151.67                                 ______________________________________                                    

                  TABLE V                                                          ______________________________________                                                             AXIAL                                                                          DISTANCE                                                         SURFACE       BETWEEN                                                    LENS  RADII(mm)     SURFACES(mm)  N.sub.D                                                                              V.sub.D                                ______________________________________                                               S1     87.132                                                            L1                      2.500       1.805 25.5                                       S2     50.967                                                            L2                      10.500      1.517 64.2                                       S3     -218.779                                                                                  0.100                                                        S4     38.314                                                            L3                      4.000       1.618 55.2                                       S5     56.924                                                                                    Z1                                                           S6     117.702                                                           L4                      1.400       1.834 37.3                                       S7     17.798                                                                                    4.702                                                        S8     -50.677                                                           L5                      1.300       1.589 61.3                                       S9     49.929                                                                                    0.100                                                        S10    27.135                                                            L6                      6.500       1.699 30.1                                       S11    -18.768                                                           L7                      1.200       1.773 49.6                                       S12    65.374                                                                                    Z2                                                     Aperture                                                                                               1.700                                                        S13    46.163                                                            L8                      4.600       1.697 48.5                                       S14    -61.782                                                                                   0.950                                                        S15    -31.839                                                           L9                      1.600       1.847 37.3                                       S16    -87.982                                                                                   Z3                                                           S17    2658.419                                                          L10                     3.500       1.806 40.7                                       S18    -45.955                                                                                   0.100                                                        S19    55.327                                                            L11                     5.400       1.487 70.4                                       S20    -30.009                                                           L12                     1.300       1.805 25.5                                       S21    -166.729                                                                                  10.527                                                       S22    93.945                                                            L13                     1.600       1.834 37.3                                       S23    37.521                                                                                    1.956                                                        S24    157.252                                                           L14                     3.500       1.786 43.9                                       S25    -74.928                                                           ______________________________________                                         ZOOM SPACING DATA                                                              EFL     Z1       Z2       Z3     BFLFVD                                        ______________________________________                                          28.88 mm                                                                               1.75 mm 20.26 mm 16.96 mm                                                                              50.66 mm 174.73 mm                             50.00  14.87    12.47    11.62  63.63177.70                                   105.00  29.25     5.24     4.47  83.17197.24                                   154.41  36.29     1.87     0.80  90.30204.37                                   ______________________________________                                    

                  TABLE VI                                                         ______________________________________                                                             AXIAL DISTANCE                                                   SURFACE       BETWEEN                                                    LENS  RADII(mm)     SURFACES(mm)   N.sub.d                                                                             V.sub.d                                ______________________________________                                               S1     155.350                                                           L1                      2.200        1.805                                                                               25.5                                       S2     62.701                                                            L2                      9.300        1.517                                                                               64.2                                       S3     -159.115                                                                                  0.100                                                        S4     47.500                                                            L3                      3.500        1.723                                                                               38.0                                       S5     73.500                                                                                    Z1                                                           S6     151.230                                                           L4                      1.504        1.834                                                                               37.3                                       S7     20.622                                                                                    5.415                                                        S8     -38.920                                                           L5                      1.400        1.598                                                                               61.3                                       S9     94.000                                                                                    0.100                                                        S10    37.400                                                            L6                      7.700        1.699                                                                               30.1                                       S11    -19.236                                                           L7                      1.100        1.773                                                                               49.6                                       S12    215.750                                                                                   Z2                                                     Aperture                                                                                               1.500                                                        S13    109.780                                                           L8                      3.300        1.743                                                                               49.2                                       S14    -144.100                                                                                  0.100                                                        S15    71.820                                                            L9                      5.800        1.589                                                                               61.3                                       S16    -37.400                                                           L10                     1.500        1.834                                                                               37.3                                       S17    -2090.000                                                                                 Z3                                                           S18    102.599                                                           L11                     3.800        1.744                                                                               44.9                                       S19    -110.900                                                                                  0.100                                                        S20    57.000                                                            L12                     5.500        1.487                                                                               70.4                                       S21    -49.500                                                           L13                     1.500        1.805                                                                               25.5                                       S22    -350.000                                                                                  10.306                                                       S23    288.000                                                           L14                     1.800        1.834                                                                               37.3                                       S24    35.570                                                                                    1.663                                                        S25    129.810                                                           L15                     3.200        1.834                                                                               37.3                                       S26    -95.800                                                           ______________________________________                                         ZOOM SPACING DATA                                                              EFL     Z1       Z2       Z3     BFLFVD                                        ______________________________________                                          39.50 mm                                                                               8.97 mm 23.72 mm 24.87 mm                                                                              55.41 mm 187.60 mm                             70.08  26.06    14.23    14.13  70.87199.93                                   137.21  42.17     5.56     4.60  90.13217.10                                   193.26  49.82     0.95     0.94  97.09223.94                                   ______________________________________                                    

                  TABLE VII                                                        ______________________________________                                                             AXIAL DISTANCE                                                   SURFACE       BETWEEN                                                    LENS  RADII(mm)     SURFACES(mm)   N.sub.d                                                                             V.sub.d                                ______________________________________                                               S1     243.578                                                           L1                      2.200        1.805                                                                               25.5                                       S2     58.863                                                            L2                      8.500        1.517                                                                               64.2                                       S3     -121.610                                                                                  0.100                                                        S4     44.309                                                            L3                      4.600        1.664                                                                               35.9                                       S5     99.626                                                                                    Z1                                                           S6     92.673                                                            L4                      1.400        1.834                                                                               37.3                                       S7     17.808                                                                                    5.358                                                        S8     -36.818                                                           L5                      1.400        1.517                                                                               64.2                                       S9     56.813                                                                                    0.100                                                        S10    27.885                                                            L6                      6.800        1.699                                                                               30.1                                       S11    -17.481                                                           L7                      1.100        1.773                                                                               49.6                                       S12    61.149                                                                                    Z2                                                     Aperture                                                                                               1.500                                                        S13    46.648                                                            L8                      4.100        1.603                                                                               60.7                                       S14    -56.897                                                                                   0.900                                                        S15    -31.060                                                           L9                      1.500        1.834                                                                               37.3                                       S16    -56.434                                                                                   Z3                                                           S17    184.516                                                           L10                     3.800        1.664                                                                               35.9                                       S18    -52.262                                                                                   0.100                                                        S19    52.773                                                            L11                     5.500        1.487                                                                               70.4                                       S20    -32.229                                                           L12                     1.500        1.805                                                                               25.5                                       S21    -157.768                                                                                  9.691                                                        S22    200.032                                                           L13                     1.800        1.834                                                                               37.3                                       S23    37.027                                                                                    1.692                                                        S24    141.797                                                           L14                     3.200        1.743                                                                               49.2                                       S25    -67.446                                                           ______________________________________                                         ZOOM SPACING DATA                                                              EFLZ1       Z2Z3          BFLFVD                                               ______________________________________                                          28.88 mm  1.00 mm                                                                         22.71 mm 19.79 mm                                                                             55.01 mm 167.60 mm                                   66.5221.03 11.5710.90     79.41192.00                                         135.0034.22  5.164.12     104.19216.77                                         193.0040.61  1.950.94     115.22227.80                                         ______________________________________                                    

                  TABLE VIII                                                       ______________________________________                                                             AXIAL DISTANCE                                                   SURFACE       BETWEEN                                                    LENS  RADII(mm)     SURFACES(mm)   N.sub.d                                                                             V.sub.d                                ______________________________________                                               S1     -781.242                                                          L1                      2.500        1.805                                                                               25.5                                       S2     156.226                                                                                   0.105                                                        S3     75.329                                                            L2                      7.473        1.487                                                                               70.4                                       S4     -728.237                                                                                  0.110                                                        S5     58.221                                                            L3                      8.716        1.491                                                                               57.2                                       S6     -1188.187                                                                                 Z1                                                           S7     64.040                                                            L4                      1.600        1.834                                                                               37.3                                       S8     18.666                                                                                    5.066                                                        S9     -63.869                                                           L5                      2.000        1.815                                                                               65.2                                       S10    18.672                                                            L6                      3.537        1.805                                                                               25.5                                       S11    56.132                                                                                    Z2                                                     Aperture                                                                                               0.800                                                        S12    40.929                                                            L7                      2.500        1.564                                                                               60.8                                       S13    -356.168                                                                                  1.575                                                        S14    -22.864                                                           L8                      1.500        1.517                                                                               52.2                                       S15    -47.470                                                                                   Z3                                                           S16    36.349                                                            L9                      7.011        1.640                                                                               60.2                                       S17    -106.713                                                                                  0.100                                                        S18    24.204                                                            L10                     6.572        1.678                                                                               55.5                                       S19    165.775                                                           L11                     1.600        1.805                                                                               25.5                                       S20    20.436                                                                                    3.220                                                        S21    48.161                                                            L12                     2.924        1.491                                                                               57.2                                       S22    -528.121                                                          ______________________________________                                         Surface S5 and S22 are aspheric                                                S5              S22                                                            ______________________________________                                         K = -1.000      D     .2551 × 10.sup.-04                                                 E     .3653 × 10.sup.-07                                                 F     .2158 × 10.sup.-11                                                 G     .5188 × 10.sup.-12                                 ______________________________________                                         ZOOM SPACING DATA                                                              EFL     Z1       Z2       Z3     BFL    FVD                                    ______________________________________                                          28.50 mm                                                                               0.71 mm 14.95 mm 18.93 mm                                                                              40.12 mm                                                                              136.62                                  50.00  16.49     7.08    11.02  48.58  145.08                                 102.00  33.46     0.83     0.30  60.60  157.10                                 ______________________________________                                    

                  TABLE IX                                                         ______________________________________                                                             AXIAL DISTANCE                                                   SURFACE       BETWEEN                                                    LENS  RADII(mm)     SURFACES(mm)   N.sub.d                                                                             V.sub.d                                ______________________________________                                               S1     195.772                                                           L1                      2.500        1.805                                                                               25.5                                       S2     67.344                                                                                    0.500                                                        S3     66.244                                                            L2                      7.000        1.613                                                                               54.6                                       S4     -411.314                                                                                  0.100                                                        S5     46.824                                                            L3                      4.000        1.834                                                                               42.4                                       S6     66.472                                                                                    Z1                                                           S7     100.775                                                           L4                      1.600        1.834                                                                               37.3                                       S8     21.211                                                                                    5.851                                                        S9     -153.496                                                          L5                      2.000        1.481                                                                               69.6                                       S10    19.263                                                            L6                      3.537        1.824                                                                               24.6                                       S11    45.706                                                                                    Z2                                                     Aperture                                                                                               0.800                                                        S12    42.808                                                            L7                      2.500        1.581                                                                               59.3                                       S13    -8183.436                                                                                 1.575                                                        S14    -24.474                                                           L8                      1.500        1.776                                                                               40.0                                       S15    -37.379                                                                                   Z3                                                           S16    35.468                                                            L9                      5.400        1.663                                                                               57.9                                       S17    -104.707                                                                                  0.100                                                        S18    26.104                                                            L10                     4.800        1.692                                                                               54.4                                       S19    238.734                                                           L11                     1.600        1.805                                                                               25.5                                       S20    23.704                                                                                    5.602                                                        S21    -402.429                                                          L12                     2.924        1.491                                                                               57.2                                       S22    -402.429                                                                                  0.200                                                        S23    107.084                                                           L13                     3.000        1.482                                                                               55.9                                       S24    -405.409                                                          ______________________________________                                         Aspheric Surface S22                                                           ______________________________________                                                D   .2455 × 10.sup.-04                                                   E   .5226 × 10.sup.-07                                                   F   -.6774 × 10.sup.-10                                                  G   .3605 × 10.sup.-12                                            ______________________________________                                         ZOOM SPACING DATA                                                              EFL     Z1       Z2       Z3     BFLFVD                                        ______________________________________                                          28.51 mm                                                                               0.71 mm 20.48 mm 18.70 mm                                                                              38.51 mm 139.51 mm                             50.00  18.89     9.95    11.04  46.17147.17                                    75.03  30.18     4.82     4.89  52.33153.33                                   102.04  38.16     1.22     0.50  56.72157.72                                   ______________________________________                                    

                  TABLE X                                                          ______________________________________                                                             AXIAL DISTANCE                                                   SURFACE       BETWEEN                                                    LENS  RADII(mm)     SURFACES(mm)   N.sub.d                                                                             V.sub.d                                ______________________________________                                               S1     122.608                                                           L1                      2.500        1.805                                                                               25.5                                       S2     55.746                                                                                    0.500                                                        S3     54.539                                                            L2                      10.600       1.517                                                                               64.2                                       S4     -249.144                                                                                  0.100                                                        S5     41.949                                                            L3                      4.328        1.702                                                                               41.2                                       S6     75.883                                                                                    Z1                                                           S7     84.733                                                            L4                      1.500        1.834                                                                               37.3                                       S8     17.252                                                                                    5.757                                                        S9     -52.546                                                           L5                      1.300        1.773                                                                               49.6                                       S10    45.963                                                                                    0.200                                                        S11    29.582                                                            L6                      6.738        1.673                                                                               32.2                                       S12    -17.554                                                           L7                      1.200        1.773                                                                               49.6                                       S13    -532.786                                                                                  Z2                                                     Aperture                                                                                               1.000                                                        S14    77.815                                                            L8                      2.452        1.834                                                                               37.3                                       S15    -58.953                                                                                   0.550                                                        S16    -34.685                                                           L9                      1.300        1.717                                                                               29.5                                       S17    -70.992                                                                                   Z3                                                           S18    33.486                                                            L10                     4.446        1.720                                                                               50.3                                       S19    -174.911                                                                                  0.100                                                        S20    37.651                                                            L11                     5.299        1.717                                                                               48.0                                       S21    -55.577                                                           L12                     2.000        1.785                                                                               26.1                                       S22    23.790                                                                                    5.147                                                        S23    -32.331                                                           L13                     2.300        1.491                                                                               57.2                                       S24    -110.442                                                                                  0.200                                                        S25    150.096                                                           L14                     6.350        1.487                                                                               70.4                                       S26    -31.538                                                           ______________________________________                                         Aspheric Surface S24                                                           ______________________________________                                                D   .1995 × 10.sup.-04                                                   E   .5118 × 10.sup.-07                                                   F   -.1442 × 10.sup.-09                                                  G   .2947 × 10.sup.-12                                            ______________________________________                                         ZOOM SPACING DATA                                                              EFL     Z1       Z2       Z3     BLFFVD                                        ______________________________________                                          28.60 mm                                                                               1.50 mm 15.87 mm 17.87 mm                                                                              41.80 mm 144.94 mm                             50.00  17.14     8.62     9.48  50.91153.87                                    75.00  26.79     4.36     4.09  56.92159.89                                   102.00  33.36     1.00     0.88  60.76163.76                                   ______________________________________                                    

Table XI sets forth the powers K1-K4 of each lens lens unit G1-G4, respectively, as a function of the geometric mean K_(M) of the extremes of the equivalent focal length of each lens where

K_(M) =√K_(S) K_(L),

and

K_(S) =the optical power of the lens at its shortest equivalent focal length, and

K_(L) =the optical power of the lens at its longest equivalent focal length.

The optical powers are the reciprocal of the equivalent focal lengths in millimeters.

                  TABLE XI                                                         ______________________________________                                         TABLE  K.sub.1 /K.sub.M                                                                          K.sub.2 /K.sub.M                                                                       K.sub.3 /K.sub.M                                                                       K.sub.4 /K.sub.M                                                                     K.sub.M                                ______________________________________                                         II     .778       -3.660  .858    1.173 .0162                                  III    .940       -4.817  1.278   1.417 .0115                                  IV     .093       -3.754  .833    1.513 .0167                                  V      .773       -3.860  .687    1.780 .0150                                  VI     .833       -4.193  1.263   1.289 .0114                                  VII    .851       -4.320  .880    1.433 .0134                                  VIII   .530       -2.156  .227    1.584 .0185                                  IX     .975       -4.000  .895    1.657 .0162                                  X      .627       -2.941  .778    1.162 .0185                                  ______________________________________                                    

Table XII sets forth the equivalent focal lengths F4 of the fourth lens units G4 of the lenses, the front vertex distance FVD₄ of the fourth lens units and the telephoto ratios TR₄ of the fourth lens units.

                  TABLE XII                                                        ______________________________________                                         TABLE       F.sub.4     FVD.sub.4                                                                               TR.sub.4                                      ______________________________________                                         II          44.35 mm    54.07 mm 1.219                                         III         61.39       71.47    1.164                                         IV          44.03       51.67    1.174                                         V           44.98       54.09    1.202                                         VI          68.21       72.36    1.061                                         VII         51.95       59.34    1.142                                         VIII        34.14       40.45    1.185                                         IX          36.75       42.48    1.156                                         X           46.58       46.58    1.162                                         ______________________________________                                    

From the foregoing tables it may be seen that

    5.0>|K.sub.2 /K.sub.m |>2.0

    1.8>K.sub.4 /K.sub.m >1.1

    1.5>TR.sub.4 >1.0

These parameters provide well corrected lenses of various ranges of equivalent focal lengths having a fourth lens unit which contributes to the compactness of the overall lens. 

Having thus described the invention, what is claimed is:
 1. In a lens having a range of equivalent focal lengths from a dimension below the diagonal of the image frame of the lens to a dimension at least substantially three times the shortest equivalent focal length where said lens comprises a first positive lens unit, a second negative lens unit, a third positive lens unit, and a fourth positive lens unit, said lens having an aperture defining means in fixed relation to said third lens unit, said first and fourth lens units being axially movable in the same direction and at least one of said second and third lens units being axially movable to vary the equivalent focal length of said lens, said second lens unit having an absolute optical power at least 2.0 as great as the geometrical mean of the extremes of the equivalent focal lengths of said lens; and

    1.8>K.sub.4 /K.sub.M >1.0

    1.5>TR.sub.4 >1.0

where K₄ is the optical power of said fourth lens unit, K_(M) is the geometrical mean of the extremes of the equivalent focal lengths of said lens, and TR₄ is the telephoto ratio of said fourth lens unit, said fourth lens unit comprising first and second sub lens units, said first sub lens unit comprising from the object end a first positive element and a doublet formed of a positive element and a following negative element, said second sub lens unit comprising a positive element most closely adjacent the image plane.
 2. The lens of claim 1 where said first and fourth lens units move in fixed relation to vary the equivalent focal length of said lens.
 3. The lens of claim 1 where said doublet is in the form of a meniscus.
 4. The lens of claim 1 where the elements of said doublet are air spaced.
 5. The lens of claim 1 where said doublet is biconvex.
 6. A zoom lens as described in claim 1 scaled to an image frame of 24×36 mm described substantially as follows:

    ______________________________________                                                             AXIAL DISTANCE                                                   SURFACE       BETWEEN                                                    LENS  RADII(mm)     SURFACES(mm)   N.sub.d                                                                             V.sub.d                                ______________________________________                                               S1     160.690                                                           L1                      2.500        1.805                                                                               25.5                                       S2     56.190                                                            L2                      10.270       1.517                                                                               64.2                                       S3     -144.312                                                                                  0.200                                                        S4     40.250                                                            L3                      4.100        1.806                                                                               40.7                                       S5     69.987                                                                                    Z1                                                           S6     61.000                                                            L4                      1.500        1.806                                                                               40.7                                       S7     15.180                                                                                    5.180                                                        S8     -40.000                                                           L5                      1.400        1.773                                                                               49.6                                       S9     49.500                                                                                    0.200                                                        S10    28.000                                                            L6                      7.200        1.673                                                                               32.2                                       S11    -15.415                                                           L7                      1.200        1.773                                                                               49.6                                       S12    -619.000                                                                                  Z2                                                     Aperture                                                                                               1.500                                                        S13    63.588                                                            L8                      3.530        1.697                                                                               48.5                                       S14    -42.087                                                                                   0.480                                                        S15    -30.682                                                           L9                      1.650        1.806                                                                               40.7                                       S16    -64.500                                                                                   Z3                                                           S17    34.420                                                            L10                     4.630        1.581                                                                               40.9                                       S18    -156.800                                                                                  0.200                                                        S19    114.940                                                           L11                     9.390        1.517                                                                               52.2                                       S20    -31.690                                                           L12                     1.220        1.805                                                                               25.5                                       S21    34.420                                                                                    2.480                                                        S22    -88.000                                                           L13                     2.400        1.806                                                                               40.7                                       S23    -38.900                                                                                   0.200                                                        S24    104.500                                                           L14                     2.860        1.806                                                                               40.7                                       S25    -140.000                                                          ______________________________________                                         ZOOM SPACING DATA                                                              EFL     Z1       Z2       Z3     BFLFVD                                        ______________________________________                                          28.83 mm                                                                               1.00 mm 19.33 mm 16.61 mm                                                                              56.93 mm 158.16 mm                             50.01  14.92    11.77    10.25  68.19169.41                                    5.01   26.31     6.24     4.38  78.01179.24                                   131.00  34.52     1.51     0.91  83.26184.48                                   ______________________________________                                    

where L1-L14 are lens elements progressively from the object to the image end, S1-S25 are the lens surfaces from the object to image end, N_(D) is the index of refraction of each lens element, and V_(D) is the dispersion of each lens element as measured by its Abbe number.
 7. A zoom lens as described in claim 1 scaled to an image frame of 24×36 mm described substantially as follows:

    ______________________________________                                                             AXIAL DISTANCE                                                   SURFACE       BETWEEN                                                    LENS  RADII(mm)     SURFACES(mm)   N.sub.d                                                                             V.sub.d                                ______________________________________                                               S1     102.879                                                           L1                      2.300        1.741                                                                               27.8                                       S2     48.694                                                                                    0.500                                                        S3     48.183                                                            L2                      10.400       1.514                                                                               64.2                                       S4     -189.534                                                                                  0.100                                                        S5     43.872                                                            L3                      4.000        1.541                                                                               47.2                                       S6     75.339                                                                                    Z1                                                           S7     84.254                                                            L4                      1.660        1.834                                                                               37.3                                       S8     20.443                                                                                    5.908                                                        S9     -32.836                                                           L5                      1.440        1.773                                                                               49.6                                       S10    57.306                                                                                    0.220                                                        S11    43.367                                                            L6                      7.200        1.717                                                                               29.5                                       S12    -16.903                                                           L7                      1.330        1.773                                                                               49.6                                       S13    -333.557                                                                                  Z2                                                           S14    64.932                                                            L8                      5.000        1.604                                                                               60.2                                       S15    -48.454                                                                                   1.126                                                        S16    -29.934                                                           L9                      2.000        1.673                                                                               32.2                                       S17    -47.916                                                                                   0.500                                                  Aperture                                                                                               Z3                                                           S18    125.580                                                           L10                     3.670        1.648                                                                               33.8                                       S19    -68.714                                                                                   0.180                                                        S20    88.886                                                            L11                     6.000        1.517                                                                               64.2                                       S21    -32.051                                                           L12                     5.500        1.785                                                                               25.7                                       S22    -83.481                                                                                   8.017                                                        S23    118.446                                                           L13                     6.000        1.581                                                                               40.9                                       S24    -42.226                                                           L14                     2.000        1.717                                                                               29.5                                       S25    37.606                                                                                    1.900                                                        S26    341.397                                                           L15                     4.800        1.805                                                                               25.5                                       S27    -95.200                                                           ______________________________________                                         ZOOM SPACING DATA                                                              EFL     Z1       Z2       Z3     BFLFVD                                        ______________________________________                                          38.50 mm                                                                               7.00 mm 19.19 mm 23.74 mm                                                                              48.36 mm 186.24 mm                             73.00  22.36    10.63    13.68  66.89201.50                                   136.00  36.30     4.64     5.02  81.83215.74                                   194.06  42.86     0.59     1.06  89.52221.97                                   ______________________________________                                    

where L1-L15 are lens elements progressively from the object to the image end, S1-S27 are the lens surfaces from the object to image end, N_(D) is the index of refraction of each lens element, and V_(D) is the dispersion of each lens element as measured by its Abbe number.
 8. A zoom lens as described in claim 1 scaled to an image frame of 24×36 mm described substantially as follows:

    ______________________________________                                                             AXIAL DISTANCE                                                   SURFACE       BETWEEN                                                    LENS  RADII(mm)     SURFACES(mm)   N.sub.d                                                                             V.sub.D                                ______________________________________                                               S1     97.471                                                            L1                      2.000        1.805                                                                               25.5                                       S2     46.414                                                                                    0.961                                                        S3     44.857                                                            L2                      7.500        1.517                                                                               64.2                                       S4     -204.325                                                                                  0.100                                                        S5     33.332                                                            L3                      5.000        1.658                                                                               50.9                                       S6     67.053                                                                                    Z1                                                           S7     48.154                                                            L4                      1.400        1.834                                                                               37.3                                       S8     16.552                                                                                    9.047                                                        S9     -29.301                                                           L5                      1.200        1.773                                                                               49.6                                       S10    37.735                                                                                    0.200                                                        S11    30.244                                                            L6                      5.800        1.673                                                                               32.2                                       S12    -13.650                                                           L7                      1.200        1.773                                                                               49.6                                       S13    -101.590                                                                                  Z2                                                     Aperture                                                                                               1.040                                                        S14    651.451                                                           L8                      2.500        1.834                                                                               37.3                                       S15    -75.022                                                                                   Z3                                                           S16    148.051                                                           L9                      2.664        1.834                                                                               37.3                                       S17    -59.655                                                                                   0.100                                                        S18    17.272                                                            L10                     3.600        1.517                                                                               64.2                                       S19    80.238                                                                                    0.570                                                        S20    -2295.605                                                         L11                     6.060        1.785                                                                               26.1                                       S21    17.700                                                                                    6.307                                                        S22    47.296                                                            L12                     2.000        1.805                                                                               25.5                                       S23    28.126                                                                                    0.931                                                        S24    29.714                                                            L13                     6.000        1.517                                                                               64.2                                       S25    -40.167                                                           ______________________________________                                         ZOOM SPACING DATA                                                              EFL     Z1       Z2       Z3     BFL    FVD                                    ______________________________________                                          35.90 mm                                                                               0.50 mm 10.79 mm 10.77 mm                                                                              49.46 mm                                                                              141.60                                  54.93   9.65     7.07     5.34  53.89  147.03                                  85.00  17.79     2.84     1.43  57.80  150.94                                 101.42  20.76     0.60     0.70  58.53  151.67                                 ______________________________________                                    

where L1-L13 are lens elements progressively from the object to the image end, S1-S25 are the lens surfaces from the object to image end, N_(D) is the index of refraction of each lens element, and V_(D) is the dispersion of each lens element as measured by its Abbe number.
 9. A zoom lens as described in claim 1 scaled to an image frame of 24×36 mm described substantially as follows:

    ______________________________________                                                             AXIAL                                                                          DISTANCE                                                         SURFACE       BETWEEN                                                    LENS  RADII(mm)     SURFACES(mm)  N.sub.D                                                                              V.sub.D                                ______________________________________                                               S1     87.132                                                            L1                      2.500       1.805 25.5                                       S2     50.967                                                            L2                      10.500      1.517 64.2                                       S3     -218.779                                                                                  0.100                                                        S4     38.314                                                            L3                      4.000       1.618 55.2                                       S5     56.924                                                                                    Z1                                                           S6     117.702                                                           L4                      1.400       1.834 37.3                                       S7     17.798                                                                                    4.702                                                        S8     -50.677                                                           L5                      1.300       1.589 61.3                                       S9     49.929                                                                                    0.100                                                        S10    27.135                                                            L6                      6.500       1.699 30.1                                       S11    -18.768                                                           L7                      1.200       1.773 49.6                                       S12    65.374                                                                                    Z2                                                     Aperture                                                                                               1.700                                                        S13    46.163                                                            L8                      4.600       1.697 48.5                                       S14    -61.782                                                                                   0.950                                                        S15    -31.839                                                           L9                      1.600       1.847 37.3                                       S16    -87.982                                                                                   Z3                                                           S17    2658.419                                                          L10                     3.500       1.806 40.7                                       S18    -45.955                                                                                   0.100                                                        S19    55.327                                                            L11                     5.400       1.487 70.4                                       S20    -30.009                                                           L12                     1.300       1.805 25.5                                       S21    -166.729                                                                                  10.527                                                       S22    93.945                                                            L13                     1.600       1.834 37.3                                       S23    37.521                                                                                    1.956                                                        S24    157.252                                                           L14                     3.500       1.786 43.9                                       S25    -74.928                                                           ______________________________________                                         ZOOM SPACING DATA                                                              EFL     Z1       Z2       Z3     BFLFVD                                        ______________________________________                                          28.88 mm                                                                               1.75 mm 20.26 mm 16.96 mm                                                                              50.66 mm 174.73 mm                             50.00  14.87    12.47    11.62  63.63177.70                                   105.00  29.25     5.24     4.47  83.17197.24                                   154.41  36.29     1.87     0.80  90.30204.37                                   ______________________________________                                    

where L1-L14 are lens elements progressively from the object to the image end, S1-S25 are the lens surfaces from the object ot image end, N_(D) is the index of refraction of each lens element, and V_(D) is the dispersion of each lens element as measured by its Abbe number.
 10. A zoom lens as described in claim 1 scaled to an image frame of 24×36 mm described substantially as follows:

    ______________________________________                                                             AXIAL DISTANCE                                                   SURFACE       BETWEEN                                                    LENS  RADII(mm)     SURFACES(mm)   N.sub.d                                                                             V.sub.d                                ______________________________________                                               S1     155.350                                                           L1                      2.200        1.805                                                                               25.5                                       S2     62.701                                                            L2                      9.300        1.517                                                                               64.2                                       S3     -159.115                                                                                  0.100                                                        S4     47.500                                                            L3                      3.500        1.723                                                                               38.0                                       S5     73.500                                                                                    Z1                                                           S6     151.230                                                           L4                      1.504        1.834                                                                               37.3                                       S7     20.622                                                                                    5.415                                                        S8     -38.920                                                           L5                      1.400        1.598                                                                               61.3                                       S9     94.000                                                                                    0.100                                                        S10    37.400                                                            L6                      7.700        1.699                                                                               30.1                                       S11    -19.236                                                           L7                      1.100        1.773                                                                               49.6                                       S12    215.750                                                                                   Z2                                                     Aperture                                                                                               1.500                                                        S13    109.780                                                           L8                      3.300        1.743                                                                               49.2                                       S14    -144.100                                                                                  0.100                                                        S15    71.820                                                            L9                      5.800        1.589                                                                               61.3                                       S16    -37.400                                                           L10                     1.500        1.834                                                                               37.3                                       S17    -2090.000                                                                                 Z3                                                           S18    102.599                                                           L11                     3.800        1.744                                                                               44.9                                       S19    -110.900                                                                                  0.100                                                        S20    57.000                                                            L12                     5.500        1.487                                                                               70.4                                       S21    -49.500                                                           L13                     1.500        1.805                                                                               25.5                                       S22    -350.000                                                                                  10.306                                                       S23    288.000                                                           L14                     1.800        1.834                                                                               37.3                                       S24    35.570                                                                                    1.663                                                        S25    129.810                                                           L15                     3.200        1.834                                                                               37.3                                       S26    -95.800                                                           ______________________________________                                         ZOOM SPACING DATA                                                              EFL     Z1       Z2       Z3     BFLFVD                                        ______________________________________                                          39.50 mm                                                                               8.97 mm 23.72 mm 24.87 mm                                                                              55.41 mm 187.60 mm                             70.08  26.06    14.23    14.13  70.87199.93                                   137.21  42.17     5.56     4.60  90.13217.10                                   193.26  49.82     0.95     0.94  97.09223.94                                   ______________________________________                                    

where L1-L15 are lens elements progressively from the object to the image end, S1-S26 are the lens surfaces from the object to image end, N_(D) is the index of refraction of each lens element, and V_(D) is the dispersion of each lens element as measured by its Abbe number.
 11. A zoom lens as described in claim 1 scaled to an image frame of 24×36 mm described substantially as follows:

    ______________________________________                                                             AXIAL DISTANCE                                                   SURFACE       BETWEEN                                                    LENS  RADII(mm)     SURFACES(mm)   N.sub.d                                                                             V.sub.d                                ______________________________________                                               S1     243.578                                                           L1                      2.200        1.805                                                                               25.5                                       S2     58.863                                                            L2                      8.500        1.517                                                                               64.2                                       S3     -121.610                                                                                  0.100                                                        S4     44.309                                                            L3                      4.600        1.664                                                                               35.9                                       S5     99.626                                                                                    Z1                                                           S6     92.673                                                            L4                      1.400        1.834                                                                               37.3                                       S7     17.808                                                                                    5.358                                                        S8     -36.818                                                           L5                      1.400        1.517                                                                               64.2                                       S9     56.813                                                                                    0.100                                                        S10    27.885                                                            L6                      6.800        1.699                                                                               30.1                                       S11    -17.481                                                           L7                      1.100        1.773                                                                               49.6                                       S12    61.149                                                                                    Z2                                                     Aperture                                                                                               1.500                                                        S13    46.648                                                            L8                      4.100        1.603                                                                               60.7                                       S14    -56.897                                                                                   0.900                                                        S15    -31.060                                                           L9                      1.500        1.834                                                                               37.3                                       S16    -56.434                                                                                   Z3                                                           S17    184.516                                                           L10                     3.800        1.664                                                                               35.9                                       S18    -52.262                                                                                   0.100                                                        S19    52.773                                                            L11                     5.500        1.487                                                                               70.4                                       S20    -32.229                                                           L12                     1.500        1.805                                                                               25.5                                       S21    -157.768                                                                                  9.691                                                        S22    200.032                                                           L13                     1.800        1.834                                                                               37.3                                       S23    37.027                                                                                    1.692                                                        S24    141.797                                                           L14                     3.200        1.743                                                                               49.2                                       S25    -67.446                                                           ______________________________________                                         ZOOM SPACING DATA                                                              EFLZ1       Z2Z3          BFLFVD                                               ______________________________________                                          28.88 mm  1.00 mm                                                                         22.71 mm 19.79 mm                                                                             55.01 mm 167.60 mm                                   66.5221.03 11.5710.90     79.41192.00                                         135.0034.22  5.164.12     104.19216.77                                         193.0040.61  1.950.94     115.22227.80                                         ______________________________________                                    

where L1-L14 are lens elements progressively from the object to the image end, S1-S25 are the lens surfaces from the object to image end, N_(D) is the index of refraction of each lens element, and V_(D) is the dispersion of each lens element as measured by its Abbe number.
 12. A lens according to claim 1 having at least one aspheric surface defined by the equation ##EQU2## where x is the surface sag at a semi-aperture distance Y from the axis A of the lens, C is the curvature of a lens surface of the optical axis A equal to the reciprocal of the radius of the optical axis, K is a conic constant.
 13. A zoom lens as described in claim 12 scaled to an image frame of 24×36 mm described substantially as follows:

    ______________________________________                                                             AXIAL DISTANCE                                                   SURFACE       BETWEEN                                                    LENS  RADII(mm)     SURFACES(mm)   N.sub.d                                                                             V.sub.d                                ______________________________________                                               S1     -781.242                                                          L1                      2.500        1.805                                                                               25.5                                       S2     156.226                                                                                   0.105                                                        S3     75.329                                                            L2                      7.473        1.487                                                                               70.4                                       S4     -728.237                                                                                  0.110                                                        S5     58.221                                                            L3                      8.716        1.491                                                                               57.2                                       S6     -1188.187                                                                                 Z1                                                           S7     64.040                                                            L4                      1.600        1.834                                                                               37.3                                       S8     18.666                                                                                    5.066                                                        S9     -63.869                                                           L5                      2.000        1.815                                                                               65.2                                       S10    18.672                                                            L6                      3.537        1.805                                                                               25.5                                       S11    56.132                                                                                    Z2                                                     Aperture                                                                                               0.800                                                        S12    40.929                                                            L7                      2.500        1.564                                                                               60.8                                       S13    -356.168                                                                                  1.575                                                        S14    -22.864                                                           L8                      1.500        1.517                                                                               52.2                                       S15    -47.470                                                                                   Z3                                                           S16    36.349                                                            L9                      7.011        1.640                                                                               60.2                                       S17    -106.713                                                                                  0.100                                                        S18    24.204                                                            L10                     6.572        1.678                                                                               55.5                                       S19    165.775                                                           L11                     1.600        1.805                                                                               25.5                                       S20    20.436                                                                                    3.220                                                        S21    48.161                                                            L12                     2.924        1.491                                                                               57.2                                       S22    -528.121                                                          ______________________________________                                         Surface S5 and S22 are aspheric                                                S5              S22                                                            ______________________________________                                         K = -1.000      D     .2551 × 10.sup.-04                                                 E     .3653 × 10.sup.-07                                                 F     .2158 × 10.sup.-11                                                 G     .5188 × 10.sup.-12                                 ______________________________________                                         ZOOM SPACING DATA                                                              EFL     Z1       Z2       Z3     BFL    FVD                                    ______________________________________                                          28.50 mm                                                                               0.71 mm 14.95 mm 18.93 mm                                                                              40.12 mm                                                                              136.62                                  50.00  16.49     7.08    11.02  48.58  145.08                                 102.00  33.46     0.83     0.30  60.60  157.10                                 ______________________________________                                    

where L1-L12 are lens elements progressively from the object to the image end, S1-S22 are the lens surfaces from the object to image end, N_(D) is the index of refraction of each lens element, and V_(D) is the dispersion of each lens element as measured by its Abbe number.
 14. A zoom lens as described in claim 12 scaled to an image frame of 24×36 mm described substantially as follows:

    ______________________________________                                                             AXIAL DISTANCE                                                   SURFACE       BETWEEN                                                    LENS  RADII(mm)     SURFACES(mm)   N.sub.d                                                                             V.sub.d                                ______________________________________                                               S1     195.772                                                           L1                      2.500        1.805                                                                               25.5                                       S2     67.344                                                                                    0.500                                                        S3     66.244                                                            L2                      7.000        1.613                                                                               54.6                                       S4     -411.314                                                                                  0.100                                                        S5     46.824                                                            L3                      4.000        1.834                                                                               42.4                                       S6     66.472                                                                                    Z1                                                           S7     100.775                                                           L4                      1.600        1.834                                                                               37.3                                       S8     21.211                                                                                    5.851                                                        S9     -153.496                                                          L5                      2.000        1.481                                                                               69.6                                       S10    19.263                                                            L6                      3.537        1.824                                                                               24.6                                       S11    45.706                                                                                    Z2                                                     Aperture                                                                                               0.800                                                        S12    42.808                                                            L7                      2.500        1.581                                                                               59.3                                       S13    -8183.436                                                                                 1.575                                                        S14    -24.474                                                           L8                      1.500        1.776                                                                               40.0                                       S15    -37.379                                                                                   Z3                                                           S16    35.468                                                            L9                      5.400        1.663                                                                               57.9                                       S17    -104.707                                                                                  0.100                                                        S18    26.104                                                            L10                     4.800        1.692                                                                               54.4                                       S19    238.734                                                           L11                     1.600        1.805                                                                               25.5                                       S20    23.704                                                                                    5.602                                                        S21    -402.429                                                          L12                     2.924        1.491                                                                               57.2                                       S22    -402.429                                                                                  0.200                                                        S23    107.084                                                           L13                     3.000        1.482                                                                               55.9                                       S24    -405.409                                                          ______________________________________                                         Aspheric Surface S22                                                           ______________________________________                                                D   .2455 × 10.sup.-04                                                   E   .5226 × 10.sup.-07                                                   F   -.6774 × 10.sup.-10                                                  G   .3605 × 10.sup.-12                                            ______________________________________                                         ZOOM SPACING DATA                                                              EFL     Z1       Z2       Z3     BFLFVD                                        ______________________________________                                          28.51 mm                                                                               0.71 mm 20.48 mm 18.70 mm                                                                              38.51 mm 139.51 mm                             50.00  18.89     9.95    11.04  46.17147.17                                    75.03  30.18     4.82     4.89  52.33153.33                                   102.04  38.16     1.22     0.50  56.72157.72                                   ______________________________________                                    

where L1-L12 are lens elements progressively from the object to the image end, S1-S24 are the lens surfaces from the object to image end, N_(D) is the index of refraction of each lens element, and V_(D) is the dispersion of each lens element as measured by its Abbe number.
 15. A zoom lens as described in claim 12 scaled to an image frame of 24×36 mm described substantially as follows:

    ______________________________________                                                             AXIAL DISTANCE                                                   SURFACE       BETWEEN                                                    LENS  RADII(mm)     SURFACES(mm)   N.sub.d                                                                             V.sub.d                                ______________________________________                                               S1     122.608                                                           L1                      2.500        1.805                                                                               25.5                                       S2     55.746                                                                                    0.500                                                        S3     54.539                                                            L2                      10.600       1.517                                                                               64.2                                       S4     -249.144                                                                                  0.100                                                        S5     41.949                                                            L3                      4.328        1.702                                                                               41.2                                       S6     75.883                                                                                    Z1                                                           S7     84.733                                                            L4                      1.500        1.834                                                                               37.3                                       S8     17.252                                                                                    5.757                                                        S9     -52.546                                                           L5                      1.300        1.773                                                                               49.6                                       S10    45.963                                                                                    0.200                                                        S11    29.582                                                            L6                      6.738        1.673                                                                               32.2                                       S12    -17.554                                                           L7                      1.200        1.773                                                                               49.6                                       S13    -532.786                                                                                  Z2                                                     Aperture                                                                                               1.000                                                        S14    77.815                                                            L8                      2.452        1.834                                                                               37.3                                       S15    -58.953                                                                                   0.550                                                        S16    -34.685                                                           L9                      1.300        1.717                                                                               29.5                                       S17    -70.992                                                                                   Z3                                                           S18    33.486                                                            L10                     4.446        1.720                                                                               50.3                                       S19    -174.911                                                                                  0.100                                                        S20    37.651                                                            L11                     5.299        1.717                                                                               48.0                                       S21    -55.577                                                           L12                     2.000        1.785                                                                               26.1                                       S22    23.790                                                                                    5.147                                                        S23    -32.331                                                           L13                     2.300        1.491                                                                               57.2                                       S24    -110.442                                                                                  0.200                                                        S25    150.096                                                           L14                     6.350        1.487                                                                               70.4                                       S26    -31.538                                                           ______________________________________                                         Aspheric Surface S24                                                           ______________________________________                                                D   .1995 × 10.sup.-04                                                   E   .5118 × 10.sup.-07                                                   F   -.1442 × 10.sup.-09                                                  G   .2947 × 10.sup.-12                                            ______________________________________                                         ZOOM SPACING DATA                                                              EFL     Z1       Z2       Z3     BLFFVD                                        ______________________________________                                          28.60 mm                                                                               1.50 mm 15.87 mm 17.87 mm                                                                              41.80 mm 144.94 mm                             50.00  17.14     8.62     9.48  50.91153.87                                    75.00  26.79     4.36     4.09  56.92159.89                                   102.00  33.36     1.00     0.88  60.76163.76                                   ______________________________________                                    

where L1-L14 are lens elements progressively from the object to the image end, S1-S26 are the lens surfaces from the object to the image end, N_(d) is the index of refraction of each lens element, and V_(d) is the dispersion of each lens element as measured by its Abbe number. 